More needs to be done to improve police investigation of sexual offences and to stop jurors being biased when cases come to court, senior legal figures said today.

The Metropolitan Police Commissioner, Sir Bernard Hogan-Howe, told reporters: "For a while, I've been concerned about how we, the police, approach and deal with sexual offences."

Sir Bernard, helping launch an independent review of the investigation of rape, said more than 80% of victims of sexual offences do not come forward, and added: "For whatever reason, people don't trust the criminal justice system to give them the assistance they need at the time they most need it."

The review will be undertaken by Dame Elish Angiolini, a former Lord Advocate of Scotland, and is part of a wider national action plan announced last week. It will be published next February.

Sir Bernard said: "This is our brave attempt to try to resolve it without someone poking us in the chest and saying, 'what are you going to do about it?'"

Of those who do come forward, 80% are vulnerable in one way or another, maybe through drink, drugs or psychiatric illness, he said.

"My concern has been whether or not the investigators are always as sensitive and empathetic to the victim's account, as they should be."

He said there had been some "awful incidents" in recent years, including the investigation into sex attacker John Worboys.

"There is some evidence we need to drastically improve how we deal with criminal investigations into rape," he said.

Director of Public Prosecutions, Alison Saunders, launching the review with Sir Bernard at Scotland Yard, said there had been some great strides over the last five to 10 years but there was a lot more to be done.

"We have seen an increase in the last few months of referrals coming through, but we need to improve the court process once the victim has decided to engage," she said.

With acquittal rates rising, there might be unconscious bias on juries. "There is a much wider debate around myths (about rape) that are in society - where do jurors come from? Society," she said.

There was nothing to stop judges warning jurors against having unconscious bias at the start of a trial, rather than waiting for the end, and she would be in favour of that happening more widely, she said.

Sir Bernard said officers had been asked to challenge themselves in terms of their possible bias when it came to stopping and searching people, so the same principle could be applied to sexual offences investigations.

Ms Saunders and Assistant Commissioner Martin Hewitt warned last week that society must reject the "out-of-date myths" about rape and the idea that a rapist is "a man in a balaclava in a dark alley".

They said a six-month investigation had uncovered "pervasive myths" about rape that exist among not only some police and prosecutors but also among society as a whole.

They said: "Despite efforts to raise awareness, many people still believe a rapist is a man in a balaclava in a dark alley, and a victim is a woman who shows her fear through fight.

"That is very rarely the case - most rapists know their victim, many victims do not physically fight and the trauma of being raped will affect each victim differently."

Last month the Crown Prosecution Service (CPS) and the Bureau of Investigative Journalism revealed that there were 2,300 rape convictions in 2013, down from 2,433 in 2010, while 129 fewer rape suspects were convicted in 2013 than in 2012.

In the last year the number of completed prosecutions and convictions has increased, the CPS has said, but the conviction rate has dropped from 63.2% in 2012-13 to 60.3% in 2013-14.

But new figures show an 8% rise in the volume of police referrals for 2013-14, compared with 2012-13, and the CPS charged 700 more defendants over the same period, an increase of 25% from the previous year.

Dame Elish said later in a statement issued by Scotland Yard: "The investigation and prosecution of rape presents uniquely challenging and sensitive issues. Overcoming these challenges requires appropriate policies, the highest levels of investigative skills and appropriate resources.

"Addressing the robust evidential requirements and any subsisting prejudice towards those who deserve the protection of the law also demands exceptional levels of preparation and advocacy. I hope this review will assist in the improvement of those processes."